Plastic polishing runner



Aug. 7, 1956 FIGJ FIG. 2

United States Patent O PLASTIC POLISHING RUNNER William F. Galey, Tarentum, Pa., assignor to Pittsburgh Plate Glass Company, Allegheny County, Pa., a Corpo- -ation of Pensylvania Application January 16, 1953, Serial No. 331,590

6 Claims. (CI. 51--195) This invention relates to materials to be used as polishing faces in the polishing of ceramic materials, such as sheet or plate glass.

In the art of polishing glass, it has been considered necessary to utilize rotational spindles upon which are mounted a plurality of felt-faced discs which are rotated in contact with the surface of the glass to be polished. The use of a very fine abrasive such as FezOs, known commonly in the art as rouge, has been used in conjunction With these felt-faced discs to assist in obtaining a finely polished glass surface.

It has been su'mised that the properties of felt which enable it to serve as a polishing medium in conjunction with slurries containing rouge include the ability of the felt to absorb or retain some rouge on or near the surface of contact between the felt face and the glass, the discontinuity of surface contact between the felt fibers and the surface being polished enabling the rouge to snear between the felt face and the glass surface, and the provision of sizeable spaces in the felt face to provide for retention of grit, small chips, etc., without their riding on the glass surface.

Although felt serves as an efl'ective polishing medium, there are several characteristics which make it undesirable to be used in the polishing of glass. Among these undesirable properties are the variability of polishing effectveness of felts due to irregular swelling when wet, excessive accumulation of rouge 011 the contact surface which necessitates periodic scraping of the felt faces, variations in the felt itself due to varying fiber lengths, strength, etc., nclusion of grit and burrs in the felt during the manufacturing process, and the poor abrasion resistance of the felt.

It has been discovered that the beneficial characteristics of felt polishers may be obtained without the inclusion of the undesirable properties of felt by the substitution of certain thermoplastic elastomers for use in forming polishing faces having high abrasion resistance. These polishng faces are formed of suitable shapes to form ridges and grooves, thereby enabiing the ridges to impart a squeegee action to the surface of glass being polished.

Accordingly, it is an object of the present invention to provide a new type of glass polisher utilzing thermoplastic elastomers having a ribbed contour of predetermined uniformity adapted to be rubbed against the surface of glass to be polished.

Another object of the present invention is to provide u means for polishing glass that utilizes a ribbed polshing surface of a thcrmoplastc clastomer that imparts a squecgee action in abrading the surface of a sheet of glass being polished by means of its relative motion against the adjacent git-rss surface and by means of its forcing an abrasive against the surface to be polished.

Still another object of the present invention is the provision of a glass polisher to be used in conjunction with slurries containing rouge wherein the polisher is provided with a discontinuous polishing surface of a thermoplastic material that does not swell when wet, that does Patented Aug. 7, 1956 not require periodic scraping, that is subject to uniform wear, that has smooth glass engaging surfaces, that has an extremely high resistance to abrasion and that does not react with Chemical reagents.

lt is still another object of the present invention to provide a runner for polishing glass having the charactcristic of being molded to a desired shape in a heating mold and to be easily remolded to the desired shape when the glass engaging surfaces are worn beyond the point ol' their maximum efficency.

These and other objects of the present invention will become apparent upon a study of the following disclosure taken in connection With the accompanying claims.

in the drawings:

Figure l is a vertical cross-sectional view of a polisher cmbodying the teaching of the present invention;

Figure 2 is a view taken along the lines 2-2 of Figure i showing one form of the configuration of ribs in the polishing face of a device in accordance with the teachings of the present invention;

Figures 3 to 7 inclusive are views similar to that of i igure 2 showing other embodiments of the present invention.

Referring to the drawings, Figure 1 shows a rotatable spindle ti) which is coupled to a motor (not shown). Attached to the lower end of the spindle is a metal dsc 12, to the lower end of which is secured a sponge rubber cushion member 14 by means of a suitable adhesive such as Minnesota Mining cement E. C. 882.

On the under side of the rubber cushioning member is attached a circular polisher 16. The latter member is provided With a plurality of ribs 18. These ribs may be arranged in a variety of ways. In Figure 2 they are shown to extend radially inwardly from the periphery of the polisher 16. An aperture 20 is provided in the center of the polisher. A tube 22 for conveying a rouge slurry to the surface being polished may be provided centrally of the rotating spindle and the amount of slurry supplied to the polished surface controlled by a valve means (not shown).

In Figure 3, the ribs 18 comprse four families of parallel ribs, each family in a separate quadrant of the circular polisher, with the central rib of each family being directed along a radius of the polisher face.

In Figure 4, the ribs 18 conprise four families of parallel ribs, wherein the ribs in each successive quadrant are alternately parallel to mutually perpendicular diameters of the polisher face.

In Figure 5, a plurality of parallel ribs are provided on the polishing face of polisher 16.

in 'Figure 6 the ribs 18 are arranged in a nanner similar to that shown in Fgure 3, except that the ribs are arranged in eight families instead of four.

In Figure 7, eight families of ribs are provided as in the Figure 6 embodiment. However, alternate families of parallel ribs are oriented normal to the radius of the center of alternate sectors between families having ribs arranged parallel to the radius at the center of the other sectors.

When glass in sheet form is passed beneath rotating ribbed polishers in the manner conventonal in the plate glass industry, a slurry of rouge is imparted to the glass surface opposing the ribs 18. Since the ribs are of a thermoplastic material, as each 'ib passes over the glass surface, a squeegee etfect is produced. This squeegee effect forces the finely divided rouge against the surface of the glass thereby smoothing out any imperfections in the glass surface rapidly. The spaces between the squeegee ribs provide areas wherein the rouge slurry may be retained in contact with the glass surface between squeegee swipes," as well as enabling grit and 3 small chips to be retained in these spaces without :narring the glass surface.

Any thermoplastic elastomer that has the rcquisite characteristics listed above is suitable for use in forming a molded plastic polisher. It is essential that these polishers have an A" type Sho'e durorneter hardness not exceeding about 70 and preferably, between about and 50, Among the substances most suitable for use as polishers are certain polyvinyl halides such as polyvinyl chloride, vinyl chloride-fiuorde copolymers, viryl chloride-acetate copolyrners, polyvinyl acetal. ,.,l, p't' pzral, butyral and polymerized mixtures of ene or in :e of the latter. Also suitable are polyethylene and tetrafluorocthylene polymers such as Teflon. Additional suitable compounds are styrenc copolymers styrenc elastomers such as "Styralov" and copolyncrs of viryl compounds with styrene polymers. for example butadiene-styrene copolymers vulcanized to improve their abrasion resistance. Other types of Organic materials are also suitable for use as polishers such as silicone elastomers. thiokol, ncoprene, and butyl ruhber. ln adtl'tion, Saran (polyvinylidene chloride), acrylonitrile resins which have been treated to improve their abrasion resistance and certain cellulose materials which are blended or plasticized with polyvinyl acetates are also suitable for use in forming the polishing runners provided they are suitably treated by either vulcanization, blending or plasticizing to form an Organic compound provider! with the desired characteristics.

in order to detet-mine the benefits teachings of the present invention, chloride having ribs deep were formed were parallel and /3" Wide. A ,6 groovc was l'ormed between the ribs. This block was fabricatcd and cemcnted onto a standard runner using a sponge rubber hacking and run continuously for 125 hours in place on a polishing assembly. At the end of this time the ribs were about /4 worn, indicating that the block would have had a life of about 500 hours. The block was examined frequently during the test, and on each occasion the feed grooves were free of caked rouge, plaster, and other contaminants that might be expected. A felt block in the same position of the polishing assembly fails to last 100 hours. Assuming a felt face block wcighing 7 /2 pounds would last for 100 hours, its rate of wear would then be .075 pound per hour. The virtyt chloridc block tested in the same position lost .002 'pound per hour indicttting a ratio of wear on a weight basis of 38:] in favor of the plztstic.

lt is believed that the improved results obtaincd using thermoplastic materials in lieu of felts is due to the fact that rouge is constantly fed to a series of clnstone;` squeegees to serve the same function as the face of a polishing felt, namely, to assure an adequate supply of the rouge being fed between the polishing face and the surface being polished.

The inclusion of the sponge rubber hacking 14 is desirable to reduce vibration as the polishers are being rotated over the glass surface. Another good eflect ob" tained by using sponge rubber is that it enables :i flexihle block to follow the contour of the glass being polshed more closely than pitch type polishers.

During expcrinentation with thermoplastic elastomer polishers, it Was observed that if the blocks were made flat by grinding, the rcmoval rate dropped off, presuntably because rouge could not be fed to the dcsired lo-- cation because of the laclt of a squcegee contact surface. Severni hloclts having squcegec contact surfaces from to in width exhibited no trouble along these lines. Also, it was found that poor removal rates were obtained when a groovcd pattern was cut into a solid block if the grooves were spaced more than an inch apart. A large number of narrow squeegees polish faster than fewer wide ones due to the increased numobtained from the polishers of vinyl molded. The ribs till l ber of interactions or swipes" between the surface being polished and the squeegee.

lt has been found that patterned plastic blocks to be used as polishers could be made very easily by using plastisols. A plastisol consists of a suspension of a powde'ed rcsin in a plasticizer, plus any other required in gredients such as stabilizer, mold release compound, or dyes. lf the plasticizer content is sufficiently high, the plastisol is liquid and may be pcnred into a mold which will yield the desired pattern. To solidify or cure the plzstiscl. it need only be heated to the curing temperature at which the resin is "dissolved" by the plasticizer. The resulting material then has all the characte-stics of the plasticized resin made by all the rnethnds. The curing temperature is preferahly 350 F. Plasticized vinyl chloride ia a tough, flexible and extremely abrasion resistant material. Each of these properties vnries With slasticizer content.

Since elastomer blocls having patterred surfaces do not have the rouge retention properties that felt does, the rate of rouge feed to ohtain optimum polishing conditions is more critical. A factor which influences the rouge feed and distribution the pattern of the block. Consistently good removal rates have been ohtained by using a block of vinyl chloride containing parts plasticizer per parts vinyl chloride /z" thick over all with parallel ribs Vs" wide and deep, ,6 wide grooves between ribs.

While the embodiments dlsclosed hereinabove describe straight rib portions 18, it is also within the purview of this invcntion to provide straight sided ribs of curved contour in order to enbance the flow of rouge slurry to all portions of the polishing face. It is recognized that eurvin;` the ribs strengthens their resistancc to bending and consequently decreases their squeegee effect. However, this arlditional strengthening can be overcome by additioral plasticizirg of the elastome', thei'eby increasing the t'endency of the curved ribs to bend 'apidly and provide the clesiretl polishing and squecgee action.

As the drawings illustrate. the ribs should be free from intersection throughout their length, thc'eby allowing the ribs freedom to tlex rapidly upon movement against the glass surface being polished. Such freedom would be irnpaired if the ribs were intersccted since intersccting the ribs along their length iinpaits the snooth, continuous, scraping etfect beneficial to po ishing. This latter effect is what is meant by the term "squecgee action" incorpo'ated in the accompanying claims.

Another be'eft obtained in using thermoplustic elas tomcrs for the polisher face instead of felt is that after the 'ibs of the polishcr face are worn, the resin may be remolded into the desired form, whereas the felt has to be removed and rep aced when worn.

The high resistance to chemical action of thez'tnoplastic elastomers makes them suitable for use in the polishing of glass wherein the mechanical polishing action is supplemented by the use of chemical agents such as hydrofluoric acid which are known to react chenically with the glass.

While only a few embodiments of the invention have been described for illustrative purposes only, it is understood that the scope ol' the invention contained hercin is to be limited only by the limitations itnposed by the appended claims. For example, thermoplastic elastoner polishing faces may be utilizcd with spider-type potishers or any other Well-known type of polisher utilizirg differcnt difierent kinds ol" rouge s urry feeds as well as the single large disc-like rotatablc polishers described hereinabove.

What is claimed is:

l. In a device for polishing a moving sheet of glass, a polisher having a face consisting essentially of a thermoplastic elastomer having an A type Shore durometer hardness between l5 and 70, said polisher face comprising at least one section having a series of narrow, parallel,

elongated ribs and grooves free from intersection throughout their length and of a width such as to enable them to impart a polishing and squeegee action to the surface being polished upon relative movement of the polishing face against said surface, the parallel grooves separating each adjacent parailel rib providing a path for passage of abrasive slurry between the polishing face and the surface worked.

2. The improvement according to claim 1, wherein the thermoplastie elastomer is polyvnyl chlorde.

3. The improvement according to claim 1, wherein the width of the ribs are from ,4 inch to inch.

4. The improvement according to claim 1 wherein the polisher face is divided into a number of sections each provided with parallel ribs and grooves extending substantialiy radiaily, wherein the ribs and grooves in each section are arranged in non-parallel relationship with the ribs and grooves of the adjacent section.

5. A glass sheet polisher apparatus comprising a rotatable spindle, a disc-like plate of relativeiy hard material attached to said spindle, a resilient hacking member attached to said plate, a polishng member of thermoplastic elastomer material having an A type Shore durometer hardness between 15 and 70 attached to said backing member, and a face opposite the surface attached to the hacking member, said face comprising at least one section having a series of narrow, arallel, elongated ribs free from intersection throughout their length and of a width References Cited in the file of this patent UNITED STATES PATENTS 369,431 Brown Sept. 16, 1887 1,800,743 Morris Apr. 14. 1931 2,426,215 Hicks Aug. 26, 1947 .FOREIGN PATENTS 26 Great Britain Jan. 4, 1865 OTH ER REFERENCES Amateur Telescope Making, published in 1946 by Munn and Co. Inc.

Prism and Lens Making by F. Twyman published 1942, obtainable from Jarrell-Ash Co., 165 Newbury St., Boston, Mass. 

1. IN A DEVICE FOR POLISHING A MOVING SHEET OF GLASS, A POLISHER HAVING A FACE CONSISTING ESSENTIALLY OF A THERMOPLASTIC ELASTOMER HAVING AN "A" TYPE SHORE DUROMETER AT LEAST ONE SECTION HAVING A SERIES OF NARROW, PARALLEL, ELONGATED RIBS AND GROOVES FREE FROM INTERSECTION THROUGHOUT THEIR LENGTH AND OF A WIDTH SUCH AS TO ENABLE THEM TO IMPART A POLISHING AND SQUEEGEE ACTION TO THE SURFACE BEING POLISHED UPON RELATIVE MOVEMENT OF THE POLISHING FACE AGAINST SAID SURFACE, THE PARALLEL GROOVES SEPARATING EACH 